Dog went stiff for about 10 minutes after a dog fight, what happened?

We have new blue heeler puppy, about 10 months old. I got home today and she and my 12 year old Papillon were excited and wanted attention. I squatted down to pet them. Pet them both. All good. I got up to put my laptop bag away and the heeler attacked the little dog. They've played fighting before, but this was more intense. Heeler's hackles were raised. I could not get the heeler off the little dog. I finally yanked her off and made her go outside. The little papillon was frozen on the floor with labored breathing, eyes bulging. I didn't know what to do. I grabbed a flat cutting board, placed her on it and took her to my bed. Wrapped her in a blanket and tried to calm her down. Continued to have labored breathing and eyes bulging for a few minutes. She tried to get up but kind of just flipped over, legs still frozen. I continued to pet her. I was on hold with the vet office at this point, because I thought maybe stroke, heart attach, broken back or something. Really had no idea. She started moving slowly after about 10 minutes. Got out of the blanket and walked to me and laid her head in my lap. She's moving now, slowly but walking around. What happened to her to freeze like that? Should I get her checked out at the vet? Do I need to worry the heeler will do that again or was it a one off, striving for attention thing? Thank you for any insight or help. - BA